The present invention is related to digital signal processing of video signals and, in particular, a digital signal processing device and imaging apparatus for processing video signals whereby an aspect ratio of a picture is converted to another aspect ratio.
Currently, there are two commercial systems for recording/reproducing a television picture based on two respective video signals: one system has 4:3 aspect ratio (based on the so-called 4:3 video signal), while the other system has 16:9 aspect ratio (based on the so-called 16:9 video signal). To use the two systems interchangeably, an aspect ratio converter has been proposed, as disclosed in Japanese Patent Application Laid Open No. 5-252538 published in 1993. According to the Published Application, the video signal in an imaging device is either converted to a different aspect ratio or is passed through unmodified. In the former case, the video signal is changed by the aspect ratio converter prior to processing by, for example, a recording/reproducing system, while in the latter case the aspect ratio converter is bypassed whereby the original (unmodified) video signal is directly supplied to the recording/reproducing system.
In the imaging device, when the aspect ratio conversion of the video signal is carried out, a so-called group delay takes place whereby the video signal is delayed for a predetermined time period prior to the subsequent processing operations in the apparatus. A problem, however, occurs when the aspect ratio conversion is either discontinued or activated: the transition between the two states causes the group delay to change in the video signal delivery to the signal processing section following the aspect ratio conversion section. As a result, the signal processing operations may not be carried out properly.
A need therefore exists for a device and method that overcomes the above disadvantage.